Archaeologists love a good mystery, and some researchers in Sweden have themselves a big one.

Earlier this year a research team opened what they believed to be the tomb of King Magnus Ladulås, who ruled Sweden from 1275-90. Magnus was a popular king with the commoners and earned the nickname “Ladulås”, which means “lock the barn”, for his law giving peasants the right to refuse free food and lodging to traveling aristocracy and clergy.

The researchers already knew the tomb was later, built by King Johan III in 1573, and now it appears that Johan chose the wrong spot. Riddarholmen Church is the traditional burial spot for Swedish royalty. One would think they’d be more careful about marking the tombs.

So where is the missing king? The team is applying for permission to dig in another tomb at the same church, which also (supposedly) contains the remains of King Karl Knutsson. Perhaps they’ll find both kings. Or perhaps they’ll find another mystery.